Investigate how varying the concentration of Sodium thiosulphate solution affects the rate of reaction with Hydrochloric Acid.

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Introduction

Affect of Concentration I am going to investigate how varying the concentration of Sodium thiosulphate solution affects the rate of reaction with Hydrochloric Acid. The equation for the reaction is: Sodium thiosulphate + Hydrochloric Acid Sodium Chloride + Water + Sulphur + Sulphur dioxide Na2S2O3(aq) + 2HCl(aq) 2NaCl(aq) + H2O(l) + S(s) + SO2(aq) This reaction has a definite end (when the cross on the test tube 'disappears'). The faster the cross 'disappears' the faster the reaction and by timing how long this takes, we can establish the rate of reaction. I predict that the greater the concentration of Sodium thiosulphate solution in the experiment, the faster the chemical reaction will take place. Therefore, the cross will disappear more quickly due to the cloudiness of the solution, but only up to a certain temperature point. After this, the solution will not react within a reasonable time because the solution will begin to decompose. I think that the concentration of a solution affects the rate of reaction because the rate of reaction depends on how frequently the molecules of the reacting substances collide. A more concentrated substance has more molecules for a given volume than a more dilute substance. ...read more.

Middle

The cross that goes beneath the beaker shall stay the same throughout the experiment, because if the cross changed, it might change in size or shape and may be harder or easier to see through the cloudy solution. In addition, the same person will have to look at the cross each time as each person can see a little differently, and someone might be able to see the cross at one point, while another cannot. Therefore, the person looking must be the same for consistency and fairness. A simple precaution to make sure not to mix up would be, careful not to mix up the measuring beakers for each of the liquids, therefore I will have three different beakers and each beaker will be labelled clearly. Apparatus Used * 3 different beakers * Conical flask * A4 paper with cross in the middle * Stopwatch Method * Get 60cm� of sodium thiosulfate solution and 5cm� of hydrochloric acid (Vary the amounts of each for the different concentration tests). * Put each solution into a different beaker and label them. * Put the 60cm� sodium thiosulfate solution and 5cm�hydrochloric acid into a conical flask and place over the cross on the paper. ...read more.

Conclusion

can see that my predictions were correct and that as the concentration of Sodium thiosulphate solution decreased, the time taken for the reaction to take place increased. In my prediction, I expected that as I added more water to the Sodium Thiosulphate solution the time it would take for the cross to disappear would lengthen. In my prediction, I expected that as I added more water to the Sodium Thiosulphate solution the time it would take for the cross to disappear would lengthen. The collision theory suggests that if the solutions of reacting particles are made more concentrated, and there are more particles in a given volume, collisions between the reacting particles are therefore more likely to occur, and rate of reaction would then go up. This statement does appear to be true as the graphs show this. Overall, the prediction I made is supported by the results of my experiment because they show that as concentration goes down, the rate of reaction time also goes down and the time for the cross to disappear lengthened. This would also support the collision theory as it states that if the solutions of reacting particles are made more concentrated, collisions between the reacting particles are therefore more likely to occur. ?? ?? ?? ?? ...read more.

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is about the right amount of time for the cross to disappear in- not too quick and not too slow. I have also decided to draw the cross on white paper. It was easiest to see when the cross had disappeared as the black cross stands out the most on the white paper.

The greater the frequency of total collisions, the greater the frequency of effective collisions. If the frequency of effective collisions increases, so does the reaction rate. Introduction/Aim In this investigation, I am finding out how concentration affects the rate of reaction between Hydrochloric acid and Sodium Thiosulphate.